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Mogas and Ethanol

Posted: Wed Sep 23, 2009 1:17 pm
by OnTheNumbers
I see Maxol are commited to to 5% ethanol blend in all of their standard unleaded this year.

What are people's experience of finding enthaol in fuel? Are there any suppliers who are not adding it to the fuel?


Posted: Wed Sep 23, 2009 3:52 pm
by Nanolight
I use E5 in the car usually. Hum gave a very good explation of it, and why you shouldn't use it in aircraft about a year ago. I'll see if I can dig up the thread..

The jist about using E5 for flying is basically, don't. :P

You will get a higher octane rating out of fuel with added ethanol in it because the ethanol increases the knock reistance of the fuel (as lead did with leaded petrol back in the day) so you can run higher compression in your engine and get more bang for your buck but it is really unsuitable for aviation purposes. And there is no discernable difference in normally aspirated or older engines without an ECU. Apparently the only difference is in forced induction cars where the ECU recognises the higher knock resistance and ups the ante of the engine.

It also has a lower calorific value so you (arguably) use more of it.

To test a fuel sample for the presence of ethanol, simply add a fe drops of water and give it a shake. If ethanol is present in the fuel the water globules will dissapear as they are dissolved by the ethanol. If they don't you have pure 100% Middle Eastern!

Posted: Wed Sep 23, 2009 3:57 pm
by Nanolight
Found it!

From Hum:

Anyone that runs unleaded petrol in their aircraft should be aware of the potential for unexpected results...

There is not an 'Avgas' equivalent quality control system in the standard of forecourt unleaded petrol. One can see all sorts of additives cleaners and 'enhancers' advertised these days. Unleaded petrol seems to smell 'different' these days also - maybe I am imagining it - anyone else notice this? I have come across a few stations in Ireland that advertise 10% ethanol in their 95 octane unleaded... Several reasons why this is not good for a light aircraft:

1. Higher vapour pressure means bubbles can form in fuel lines and pumps when you don't expect it to - eg low pressure warm days - esp at high altitude.

2. More heat required to vapourise ethanol means increased likelihood of carb icing..

3. Ethanol might not be good for some of the components of your fuel system - think about rubber component of the engine - driven fuel pump, seals, any non-metal pipes etc...

The regs are there as a result of years of hard lessons... stick to them...

Don't fly above 6000 ft on unleaded 'car' petrol (mogas)
Don't allow mogas in tanks to get above 20 Deg C
Don't use fuel with ethanol (there is an easy test.. look it up in the links below)

If you have 2 tanks think about using Avgas for take-off and landing and switch to the cheap stuff in the cruise.

Read about mogas and ethanol in general on these websites:

UK position here

Irish position here ... =185&a=493

aeronautical notice here:

Good US site and source of most of the mods here: ... ation.html

Posted: Wed Sep 23, 2009 5:16 pm
by OnTheNumbers
Hmm, thanks for putting that altogether Nano but I think I really didn't make my question clear.

I knew about the issues of enthanol in fuel, what I was hoping was that someone could tell me if they know which particular brands are adding ethanol, or more usefully, which petrol is clear of the stuff.

BTW according to the LAA, the test you mentioned is only reliable for >5% alcohol mix. Apparently to do a reliable test you need one of these kits. ... 1353-p.asp


The point is...

Posted: Wed Sep 23, 2009 6:51 pm
by hum
or more usefully, which petrol is clear of the stuff
Just because someone says on a website that X fuel has or has not got ethanol is not a basis for using it in your aircraft. I would say that the ONLY way to ensure that unleaded forecourt fuel you put in your aircraft is ethanol free is to test it yourself :)

Posted: Wed Sep 23, 2009 9:38 pm
by OnTheNumbers
I'm in agreement with you about positive testing but at the same time but if someone knows that a particular brand (like the Maxol example I mentioned) is definitely using ethanol all of the time, I don't need to bother testing their fuel - I can eliminate it out of hand.


Posted: Thu Sep 24, 2009 1:35 am
by Racecrest Aviation
Hi On the numbers, I can add a cent r 2 to this thread, I have researched this extensively as i have a newly established RTF and flying club at EINC where we are running 2 Rotax 912s and the 1 Jabiru engined NG4's, I also spend alot of time crossing the pond 2 UK demoing our Aircraft.

I decided to talk to all fuel distributors in Ireland to setup a delivery service to eliminte this jerry can syndrome..! (hate it, it terrifies me), and unfortunatly none of them were prepared to commit to what actually was the breakdown of their fuel as it changes quite regularly (additives) by the time it reaches the pumps etc and none produced ethanol free fuel.

However fear not the only company that will garantee they are still taking aim at the local tree hugger/eco mentalist..! :) is BP. They provide 98 premium which reduces the knock factor and for my particular uses is by far the best fuel in my opinion.

Although not available down south it can be bought in Newry as this is the closest station. As a result of this I bought a 2000 litre certified bowser nuff said :) and did a deal with the manager who is prepared to give me in writing what the fuel is (every time I come in and filler up..!) and that bp dont use any ethanol or ethanol based products in their fuel. Nuff said.

C ya :)

Posted: Thu Sep 24, 2009 9:02 am
by C152
Nice plug Mark :mrgreen:

Posted: Thu Sep 24, 2009 9:55 am
by Racecrest Aviation
not intended as a plug merely highlighting the fact to why I needed to find the most reliable ethanol free fuel source for my endeavours, I could think of better places to "plug" I assure you..! Now have you anything constructive to add with your vast flying experience to this thread?

Posted: Thu Sep 24, 2009 11:47 am
by C152
Back in the pram :roll:

Re: Mogas and Ethanol

Posted: Tue Jan 05, 2010 3:23 am
by Jim
@On the numbers
Afraid you need to go north.
"At the moment, there are two fuels which don't have alcohol/ethanol added. These are 'BP Ultimate 97' and 'Shell V Power' (also 97)."
It seems there is no Southern equivalent now that Estuary and Mocal have added it too!

Re: Mogas and Ethanol

Posted: Tue Jan 05, 2010 10:34 am
by Pilot
I keep hearing that the days of Avgas are numbered (seems to be true).

Are we also saying that the days of mogas usable in aircraft are numbered too, with ever reducing availability of suitable mogas?

Not a pretty picture!

Re: Mogas and Ethanol

Posted: Tue Jan 05, 2010 2:22 pm
by Bluebeard
I recently did a little test with Maxol petrol advertised as having 5% ethanol, and Esso regular unleaded.

First I carefully did the test-tube procedure, adding petrol to about 10% water and shaking, then seeing whether the interface between the water and the petrol moved. Neither Maxol nor Esso tested positive, on several tests.

Then I got Airworld's test kit and tested the two petrols again. This time the Maxol stuff immediately gave a positive result, while the Esso tested negative.

I would conclude that the test tube procedure does not reliably test whether there is a low level of ethanol in the petrol, its main merit may be to show (if circumstances require!) that you did check your mogas for ethanol using an approved procedure.

Re: Mogas and Ethanol

Posted: Tue Jan 05, 2010 5:41 pm
by stovepipe
Hi all,
Perhaps a case exists to change the student pilot (and engineer) syllabus to include ethanol testing as well as water testing.I know how hard it is to get people to remember to test the fuel at all, not to mind add an extra test.Should the IAA put out a Notice about ethanol, given that several hundred people in the aviation community use Mogas for sport flying?

Re: Mogas and Ethanol

Posted: Sun Jan 10, 2010 5:01 pm
by cubpilot
The fuel crisis of the 1970s saw a lot of supposedly dangerous and illegal (as far as the CAA were concerned) flying being done on Mogas. It took Dick Stratton of CSE and BGA to do about 100hrs well documented hours on a Beagle Airdale plus supporting data from those of us he knew who were using mogas to prove to CAA that mogas was not detrimental.
Todays authorities are taking the same stance on ethanol content. I would suggest that everyone using mogas keep records of all flight hours on mogas and cross reference to where it has been obtained.
I am reliably informed that when supplies were short much of the fuel in use in WW2 had significant ethanol content so I very much doubt if there will be any increase in incidents relating to this change in fuel spec.

Before mogas was approved I took a friend who was quite high up in CAA for a flight and casually remarked on how nicely the engine was running on mogas. the look of horror was priceless but once on the ground again it dawned on him the plane had not fallen out of the sky.

As a caveat, the only time i have experience vapour lock happened when the cub was on 100% avgas but the oat during refueling had been 39C.